The world of the play is its cultural and historical context as well as the characters' situation and relationships. Old plays can be reinterpreted and their time and setting changed.
When you’re writing about context, you’re not meant to provide a history lesson. It may be necessary to provide a historical fact, but it should be linked to a point that you are making about the production under discussion. Think about the speech that Mr Birling gives at the dinner table in An Inspector Calls.
You could write:
For the post Second World War audience who know he is wrong, Mr Birling seems complacent and misguided as he claims that there will never be a major world conflict. Priestley has created a dramatic situation in which the audience expect Mr Birling to be punished for his arrogance.
You shouldn’t write:
The First World War ran from 1914-1918 and the Second World War ran from 1939-1945. Mr Birling speaks before these events.
Your facts are still correct in the second version but you’re not connecting them with the theatrical effect. Remember that in writing about performance, just as with any other kind of writing, you must connect your point and your proof and make appropriate comments.
Now watch this clip that explores J B Priestley’s social and political influences. This background knowledge should give you more insight into what the play is really about. You should always consider what motivated the playwright to create the work and respect their intentions when performing it.